Promise.all for parallel execution in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run multiple promises in parallel using Promise.all.

Node.js

const promise1 = Promise.resolve(3);
const promise2 = Promise.resolve(5);

Promise.[1]([promise1, promise2])
  .then(results => {
    console.log(results); // [3, 5]
  });

Drag options to blanks, or click blank then click option'

Aall

Brace

Cany

Dresolve

Attempts:

3 left

💡 Hint

Common Mistakes

Using Promise.race instead of Promise.all

Using Promise.resolve which does not accept an array

Promise.all runs all promises in parallel and waits for all to resolve.

2fill in blank

medium

Complete the code to handle the results of Promise.all with async/await syntax.

Node.js

async function fetchData() {
  const results = await Promise.all([1]);
  console.log(results);
}

fetchData();

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AfetchUser() && fetchPosts()

BfetchUser(), fetchPosts()

C[fetchUser(), fetchPosts()]

D{fetchUser(), fetchPosts()}

Attempts:

3 left

💡 Hint

Common Mistakes

Passing promises separated by commas without array brackets

Using curly braces instead of square brackets

Promise.all expects an array of promises as input.

3fill in blank

hard

Fix the error in the code to correctly catch errors from Promise.all.

Node.js

Promise.all([promiseA, promiseB])
  .then(results => {
    console.log(results);
  })
  .[1](error => {
    console.error('Error:', error);
  });

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Afinally

Bcatch

Cthen

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using then instead of catch for error handling

Using finally which runs regardless of success or failure

The catch method handles errors from promises.

4fill in blank

hard

Fill both blanks to create a function that runs two async tasks in parallel and returns their results.

Node.js

async function runTasks() {
  const results = await Promise.[1]([task1(), task2()]);
  return results.[2](result => result * 2);
}

Drag options to blanks, or click blank then click option'

Aall

Bmap

Cfilter

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter or reduce instead of map for transforming results

Using Promise.race instead of Promise.all

Promise.all runs tasks in parallel. Then map doubles each result.

5fill in blank

hard

Fill all three blanks to create a function that fetches user data and posts in parallel, then logs user name and post count.

Node.js

async function fetchUserData() {
  const [[1], [2]] = await Promise.[3]([getUser(), getPosts()]);
  console.log(`User: ${user.name}, Posts: ${posts.length}`);
}

Drag options to blanks, or click blank then click option'

Auser

Bposts

Call

Drace

Attempts:

3 left

💡 Hint

Common Mistakes

Using Promise.race which resolves on first promise

Not destructuring the results array

Destructure results as user and posts. Use Promise.all to run both fetches in parallel.